RHA Newsletter (1971)

INTERESTING HAPPENINGS WITH GIBBERELLIC ACID TREATMENT
by Ivan Rawlinson
Andover, England

In the summer of 1969 a bush hybrid tea rose, 'Anvil Sparks,' (coral-red, with splashes of yellow stripes and spots) was affected with mildew, followed by a serious attack of die-back. The wood was pruned out to a few inches above the ground level.

The next move was to bring into use gibberellic acid, an extract from the Japanese fungus, Gibberella fujikuroi. Its main use has been to increase the yield or to advance the harvest of fruit crops such as grapes, pears, strawberries and clementines.

After seeing an article in one of our garden publications by a reader who injected his plants in what must have been a very slow process, I decided to fix up a drip method similar to a blood-transfusion. The hypodermic needle was inserted as in budding, and held in place by a rubber budding band. The gibberellin was in solution, 100 mg. to one pint of rain water. A rubber tube was connected from the container to the needle with a small glass tube to observe the supply which was controlled by a metal screw pinch-cock. The rate of flow of gibberellin was one drop every five minutes.

Fourteen days after the treatment commenced, growth reached three feet, but more surprises were to follow... In the first flush of bloom roughly half the number of roses were of the 'Anvil Sparks' colouring. The others were different shade and had no stripes. These first sports were yellow at the base of the petals inside and out, and at the half-opened stage of bloom the roses were very luminous. From then on the bush began to produce more and different-coloured sports. And the various sports looked like different ancesters in the pedigree of 'Anvil Sparks'!

Blooms of the first sports, just described, were forwarded to two of our well-known nurserymen for identification. One said it was the H.T. 'Bettina'. The other named it as the H.T. 'Cover Girl'. Since both nurserymen grow 'Anvil Sparks', I drew Mr. Graham Stewart Thomas attention to what was happening. He put me in touch with Herr Wilhelm Kordes who had introduced it into the United Kingdom from South Africa.

The sorting out of the pedigree was under way and most of the family shades have appeared since this bush started to sport. 'President Herbert Hoover', 'Texas Centennial', and two yellow-shaded blooms have appeared. The last sport appeared during the summer of 1971.

Perhaps the most important colour has been copper-red inside and old-gold outside of the petals. Could this be Rosa foetida bicolor? I think it may be, through the variety 'Souvenir De Claudius Pernet', which appears in the pedigree. There are 35-38 petals in number as in the first sport described.

An interesting point is the appearance of a deep-pink shade on one or two petals of the fully open bloom, both on the photograph transparency and the colour prints; no doubt a hint that 'President H. Hoover' was to follow.

Dr. J. Stubbs of I.C.I., who supplied the Gibberellin was kept informed of the happenings. He could understand the rapid growth that was made, and that vegetative cell division had taken place, but wonders at the cause of so many colour changes that took place. He thought that perhaps this was due to the plant growing in such a poor state of health at the time of gibberellic acid treatment, the slow drip method of treatment, and not giving the recommended dilution of the gibberellin. (I gave 100 mg. to one pint of rain water, and the recommended strength is 100 mg. to one litre of water.)

The first sport appeared at Dorneywood, the official country residence in Buckinghamshire of the Foreign and Commonwealth Secretaries. At that time the Foreign Secretary was Rt. Hon. Michael Stewart C.H. who took a very great interest in all that was taking place.

I feel certain that when more is known about this fungal extract it will prove to be of great importance in rose growing and in food production.

Best wishes to the R.H.A. and its members,

Sincerely,
Ivan Rawlinson